It was not so much that Peter had denied Jesus three times but it gives us a better look at the Greek meanings of Peter three responses to his love for Jesus.
The first was a reply was agapao love or “to love deeply”, that is what the law demands.
The second reply in Greek means “to be fond of”, phileo. A love of a lesser degree than the first, as between friends.
Now Jesus in the first two uses the Greek love word as agapeo . In knowing Peter feeling ashamed and Peter feeling his own weakness.
In this way He was showing Peter it is okay, your sin in wiped clean. And in the final reply Peter has Jesus asurrance that He still has great plans for Peter when He says ” Feed my sheep”
It was now up to him and the other apostles to build the church for the Kingdom of God !!